The present invention relates generally to detergent or cleansing compositions in viscous liquid or gel-like form which possess thixotropic properties. More specifically, the present invention relates to a kaolinite clay additive for imparting thixotropic properties to such compositions and, more particularly, to liquid automatic dishwasher detergent compositions incorporating a kaolinite clay thickening agent for imparting thixotropic properties thereto.
Thixotropic cleansing and detergent compositions suitable for various applications are well known in the art. Commercially available cleansing and detergent compositions typically incorporate therein certain expandable layered clays, i.e., aluminosilicates or magnesium silicates, which exhibit the ability of the layered clay structure to swell or expand on contact with water. Clays commercially available as thixotropic agents are those clays classified geologically as smectites (or montmorillonoids) and attapulgites (or polygorskites). Smectites are three-layered clays having a layered sheet structure composed of two layers of silica tetrahedrons with a central layer of aluminum oxide in a dioctahedral crystal lattice and/or magnesium oxide in a trioctahedral crystal lattice. Such clays include montmorillonite (bentonite), beidellite, nontronite, volchonskoite, hectorite, saponite, sauconite and vermiculite. Attapulgites have a chain structure composed of chains of silica tetrahedrons linked together by octahedral groups of oxygens and hydroxyls containing aluminum and magnesium atoms.
Such clays are chemically available under various tradenames, such as, for example, Korthix, a bentonite clay from Georgia Kaolin Company, Inc. of Union, N.J.; Gelwhite GP, H, etc., a bentonite clay from E.C.C. America, Inc. of Atlanta, Ga.; Bentone EW, a highly processed hectorite clay from NL Chemicals, Inc. of Hightstown, N.J.; and Attagel 40, 50, etc., which are attapulgite clays from Engelhard Minerals and Chemicals Corporation of Edison, N.J.
The use of such smectite and/or attapulgite expandable clays in abrasive false-body fluid phase scouring cleanser compositions is disclosed in U.S. Pat. No. 3,985,668. As discussed therein the scouring composition comprises a relatively heavy, water-insoluble particulate material and a relatively light, water-insoluble particulate filler, both of which are suspended throughout a continuous false-body fluid phase formed by admixing an aqueous liquid with an inorganic colloid-forming agent which is present in a concentration ranging from about 1% to 10% by weight of the total composition. The clays disclosed in U.S. Pat. No. 3,985,668 as suitable for use as the inorganic colloid-forming agent are the expandable smectites and attapulgites hereinbefore mentioned.
It is also well known to use such inorganic colloid-forming smectite and/or attapulgite as thickening or suspending agents in liquid automatic dishwater detergent compositions in order to impart desired rheological properties to the composition. For example, U.S. Pat. No. 4,226,736 discloses a low-foaming machine dishwashing composition comprising an aqueous thickener, a non-ionic surfactant and water, in the form of a gel having a minimum yield point of at least 1170. The aqueous thickener is disclosed as being present in amount ranging from about 0.1 to 20 percent by weight of the total composition. Examples of composition formulations are presented in U.S. Pat. No. 4,226,736, incorporating Bentonite BC, a bentonite clay marketed by American Colloid Co., thickened with organic ammonium ions by admixing therewith triethanolamine, and Hi-Gel, also a bentonite clay consisting essentially of all montmorillonite.
A liquid automatic dishwater detergent (LADD) composition containing chlorine bleach and having thixotropic properties is presented in U.S. Pat. No. 4,740,327. The basic dishwater detergent formulation disclosed has a pH of about 10.5 to 13.5 and comprises approximately by weight: 8 to 35% sodium tripolyphosphate as a detergency builder; 2.5 to 20% sodium silicate as an alkalinity agent; 0 to 9% sodium carbonate as an optional alkalinity enhancing agent: 0.1 to 5% chlorine bleach stable defoamer/surfactant; 0.1 to 5% chlorine bleach stable, water-dispersible organic detergent active material; sodium hypochlorite in an amount sufficient to provide about 0.2 to 4% of available chlorine: a thixotropic thickener in an amount sufficient to provide the composition with a thixotropy index of about 2.5 to 10; and water in an amount effective to avoid destruction of the desired thixotropic properties, typically from about 45% to 75% by weight of the composition. The preferred thixotropic thickeners are stated to be the inorganic, colloid-forming clays of smectite and/or attapulgite types such as those disclosed in U.S. Pat. No. 3,985,668, and are generally presented in an amount ranging from 1.5 to 10% by weight of the composition, and preferably in an amount ranging from 2 to 5% by weight of the composition.
Variations of the basic thixotropic LADD formulation of U.S. Pat. No. 4,740,327 are presented in U.S. Pat. Nos. 4,752,409; 4,801,395 and 4,836,946. The incorporation of small amounts, such as 0.08 to 0.4 weight percent, of calcium, magnesium, aluminum or zinc stearate or other polyvalent metal salts of long chain fatty acids having 8 to 22 carbon atoms is disclosed in U.S. Pat. No. 4,752,409 as improving the physical stability of liquid gel-like compositions including thixotropic thickeners such as montmorillonite, attapulgite and hectorite-type clays. In U.S. Pat. No. 4,801,395, it is disclosed that the physical stability of such formulations may also be improved by incorporating into the composition small amounts, such as 0.02 to 0.4 weight percent, of long chain fatty acids having from 8 to 24 carbon atoms. Additionally, it is disclosed in U.S. Pat. No. 4,836,946 to add from 0.01 to 0.5% by weight of an alkali metal or ammonium fatty acid salt as a means to increase the apparent viscosity and physical stability of such a thixotropic LADD composition.
Although such expanding layer smectite and attapulgite type colloid-forming clays have proven effective as agents for imparting thixotropic properties to liquid or gel-like detergents or cleaners, in particular liquid automatic dishwater detergent compositions, they must be shipped as dry, particulate solids rather in the preferred form of a high solids aqueous slurry or dispersion, because of the extremely high viscosities associated with slurries or dispersions of such expanding smectite and attapulgite type colloid-forming clays even at low to moderate solids level. Accordingly, it is conventional commercial practice to ship such smectite and/or attapulgite clay based thickeners as a dry, particulate material and mix these thickeners with water just prior to usage to form a low solids, highly viscous aqueous dispersion typically at a solids level less than about 15% by weight and generally in the range of 5 to 10% solids by weight. This low solids, highly viscosity dispersion of smectite and/or attapulgite clay thickener is then added to the aqueous detergent or cleaner composition, typically as the last ingredient, to impart the desired thixotropic properties to the composition.
It would be advantageous to have a thickening or suspending agent for adding to an aqueous composition for imparting thixotropic properties thereto, which agent could be used as a relatively low viscosity, high solids aqueous slurry or dispersion at a solids level of at least 50% by weight, and preferably also shippable as a high solids aqueous slurry at a solids level at least 65% by weight. Having thickening agent that could be added to an aqueous composition as a high solids slurry would be advantageous in that additional water could be utilized in forming the basic aqueous composition to facilitate the dissolution of detergency builders, alkalinity agents and other components without exceeding overall water content limits upon addition of the thixotropic thickening agent. Further, the dust control problem and other handling problems associated with the use of a dry, particulate material would be avoided if the thickening or suspending agent could be shipped as a high solids aqueous slurry or dispersion. Further, the use of the high solids aqueous slurry or dispersion would eliminate the need for a separate make-down stage required of the dry, particulate materials.
Accordingly, it is an object of the present invention to provide a thickening or suspending agent for imparting thixotropic properties to an aqueous composition, which agent may be utilized in the form of a high solids aqueous slurry.
It is a further object of the present invention to provide such a thickening or suspending agent which may also be shipped as a high solids aqueous slurry.
It is an additional object of the present invention to provide a detergent or scouring composition incorporating such a thixotropic thickening or suspending agent.
It is a still further object of the present invention to provide a detergent composition incorporating such a thixotropic thickening or suspending agent, which composition is suitable for use as a liquid automatic dishwasher detergent.